I am calling a third party api and the request using feignClient gives 400 Bad request error

public interface NameMatchClient {

    @PostMapping("/v1/name/match")
    ResponseEntity<NameMatchResponseDto> matchNames(
            @RequestBody NameMatchRequestDto nameMatchRequestDto
    );

}

feign.FeignException$BadRequest: [400 Bad Request] during [POST] to [https://demo.com/v1/name/match] [NameMatchClient#matchNames(NameMatchRequestDto)]: [{"data": null, "message": "Bad Request Error", "status": "error"}] at feign.FeignException.clientErrorStatus(FeignException.java:213) at feign.FeignException.errorStatus(FeignException.java:194)

Whereas while using restTemplate, I am getting back response successfully.

            MultiValueMap<String, String> formData = new LinkedMultiValueMap<>();
            formData.add("pan_name", aadhaarName);
            formData.add("pan_name_combined", aadhaarName);
            formData.add("bank_name", bgvName);

            HttpEntity<MultiValueMap<String, String>> entity = new HttpEntity<>(formData, headers);

            ResponseEntity<NameMatchResponseDto> responseEntity = restTemplate.exchange("https://demo.com/v1/name/match", HttpMethod.POST, entity, NameMatchResponseDto.class);

what is the reason behind this behaviour?